KR20170054985A - Method and apparatus for performing handover based on beamforming - Google Patents

Abstract

The present invention provides a method for performing a handover for a communication device mounted on a mobile body by a base station. The base station measures timing advance (TA) using a signal received from the communication device. The base station determines whether the mobile body enters a handover zone by using the measured TA. The base station reduces a reference signal received power (RSRP) averaging period for averaging RSRP from a first value into a second value when the mobile body enters the handover zone. According to the present invention, a handover success rate can be improved in a cell, to which beamforming is applied.

Description

[0001] METHOD AND APPARATUS FOR PERFORMING HANDOVER BASED ON BEAMFORMING [0002]

The present invention relates to a method and apparatus for performing handover based on beamforming.

In a cellular mobile communication system, a terminal is connected to a cell during a stop or movement to perform communication. An example of when the terminal is moving is as follows. Many users can connect to an external cell using their own terminal in a moving body moving at a high speed like a train. For example, the terminal may connect to a base station of a third or fourth generation mobile communication system to make or receive a telephone call or connect to the Internet. In another example, people in a mobile (e.g., a train) may connect to a Wi-Fi access point in the mobile using a personal terminal. In this case, there is a need for a separate mobile communication device (for example, a communication device for a vehicle) that connects to an external cell to collect data of a plurality of terminals and transmits the collected data to an external cell. Examples of former can be categorized into one hierarchical communication, and examples of the latter can be categorized into two hierarchical communication.

When the user terminal directly connects to the cell or when the vehicle communication device connects to the cell, the mobile terminal or the mobile communication device must perform a handover from one cell to another.

The performance of the handover is very important when the cell for the moving object uses beamforming. If the handover is not successfully performed at the correct timing, data loss may occur. There is a need for a handover method that can be usefully used when a base station or a mobile terminal (vehicle communication device) forming a cell uses beamforming.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and apparatus for improving handover success rate in a cell to which beamforming is applied.

According to an embodiment of the present invention, a method is provided for a base station to perform a handover for a communication device mounted on a moving body. The base station handover method includes: measuring a timing advance (TA) using a signal received from the communication device; Determining whether the mobile has entered a handover zone using the measured TA and the reference TA; And decreasing an RSRP averaging period for averaging a reference signal received power (RSRP) from a first value to a second value when the mobile unit enters the handover zone.

The step of determining whether the moving object has entered the handover zone may include determining a moving direction of the moving object based on the measured variation pattern of the TA.

Wherein the step of determining the moving direction of the moving object comprises the steps of: when the measured variation pattern of the TA indicates that the measured TA decreases with time, Determining that the antenna is moving toward the antenna; And determining that the moving object is moving away from the first antenna when the measured variation pattern of the TA indicates that the measured TA increases with time.

Wherein the step of determining whether the mobile has entered the handover zone comprises the steps of: when the mobile moves toward a first antenna for a first cell connected to the communication device and the measured TA is smaller than the reference TA, And determining that the mobile has entered the handover zone.

The reference TA can be determined according to the moving speed of the moving object.

The first antenna may be a beam-forming antenna for the moving object.

The second value may have a smaller value as the moving speed of the moving object is higher.

The reducing the RSRP averaging period may include informing the communication device that the mobile has entered the handover zone to reduce the RSRP reporting period of the communication device.

Decreasing the RSRP averaging period comprises: resetting a first timer; And determining, using the first timer, whether the communication device has successfully handed over from the first cell to the second cell within a time corresponding to twice the reference TA.

The handover method of the base station may further include reducing the RSRP averaging period to the first value when handover of the communication apparatus is successful.

Wherein the handover zone is configured such that the strength of the signal received from the first cell connected to the communication device to the communication device is equal to the strength of the signal received from the second cell neighboring the first cell to the communication device Can be set based on the intersection point.

The measuring step; Measuring a first TA based on a random access preamble received from the communication device; And measuring a second TA based on a sounding reference signal (SRS) received from the communication device.

The step of determining whether the mobile has entered the handover zone may include determining a moving direction of the moving object using the first TA and the second TA.

According to another embodiment of the present invention, there is provided a method for performing a handover on behalf of a plurality of terminals existing in a moving body, the communication apparatus mounted on the moving body. Wherein the handover method of the communication apparatus comprises: transmitting at least one of a random access preamble and a sounding reference signal (SRS) to a base station for TA (timing advance) measurement; And reducing a reference signal received power (RSRP) report period from a first value to a second value when it is determined that the mobile has entered a handover zone based on the measured TA.

The step of reducing the RSRP report period may include determining whether the mobile has entered the handover zone using a reference TA determined according to the moving speed of the moving object and the measured TA.

Wherein the handover method of the communication device further comprises a step of, prior to the reducing step, determining whether the communication device has a first antenna for a first cell and a second antenna for a second cell neighboring the first cell, And receiving the cell coverage TA from the base station.

The handover method of the communication apparatus may further include reducing the RSRP report period to the first value when the handover is successful within a predetermined time.

The predetermined time may correspond to twice the reference TA.

According to yet another embodiment of the present invention, a base station is provided. The base station comprising: a memory; And a processor connected to the memory and performing a handover for a mobile entity in which a plurality of terminals exist.

The processor may receive at least one of a random access preamble and a sounding reference signal (SRS) from a communication apparatus mounted in the moving body.

The processor can measure a timing advance (TA) using the received signal.

The processor determines whether or not the mobile has entered a handover zone for performing a handover from the first cell to the second cell using a reference TA determined according to the moving speed of the moving object and the measured TA can do.

The processor may reduce an RSRP averaging period for averaging a reference signal received power (RSRP) from a first value to a second value when the mobile device enters the handover zone.

The processor can determine whether the handover of the communication device is successful within a first time corresponding to twice the reference TA.

The processor may return the RSRP averaging period to the first value if a handover of the communication device succeeds within the first time or the first time has elapsed.

According to the embodiment of the present invention, the handover success rate can be increased in a cell environment in which a base station and a terminal use an antenna to which beamforming is applied, thereby reducing data loss.

Also, according to an embodiment of the present invention, a handover method that is easily applied to a mobile wireless backhaul for a high-speed group moving object (e.g., a subway, a high-speed train, a bus, etc.) moving at a high speed can be provided.

Also, according to the embodiment of the present invention, a beam forming technique having a high antenna gain can be applied to a mobile communication system using a millimeter wave as a carrier. Accordingly, a handover method that is easily applied to a mobile communication system using a high frequency can be provided.

Unlike the cell boundary characteristics of a cell using a microwave frequency band, power crossing characteristics of a home cell and a neighboring cell are very different at a cell boundary of a cell using a high frequency band. According to an embodiment of the present invention, a handover can be performed at a point of time that is as close as possible to a power intersection of a cell boundary that the cell can have. This can reduce data loss that may occur during handover.

1 is a diagram illustrating a handover procedure for explaining a handover interruption time.
FIG. 2 is a diagram illustrating a cell configuration scenario when beamforming is applied to an RF and antenna for a group mobile station according to an embodiment of the present invention. FIG.
3 is a three-dimensional representation of an antenna beam pattern.
FIG. 4 is a diagram showing a secondary representation of the beam pattern of FIG. 3. FIG.
5 is a graph showing the power distribution when the height of the antenna installed on the ground is larger than the height of the receiving antenna provided on the mobile body.
FIG. 6 is a diagram showing a case where the power distribution of FIG. 5 is enlarged.
FIG. 7 is a diagram illustrating a signal intensity of a home cell and a signal intensity of a neighboring cell that change according to movement of a group moving body.
FIG. 8 is a diagram illustrating a cell configuration scenario when beamforming applied RF and antennas are used for group moving bodies according to another embodiment of the present invention. FIG.
FIG. 9 is a diagram illustrating a signal strength of a home cell and a signal strength of a neighboring cell that change according to movement of a group moving object in the cell configuration scenario of FIG. 8. FIG.
FIG. 10 is a diagram illustrating a case where a handover zone is set in a region where power (or signal strength) of a home cell is drastically reduced according to an embodiment of the present invention.
11 is a diagram illustrating a case where a handover zone is set in a region where the power of the home cell is gradually reduced but the power of the neighboring cell is rapidly increased according to an embodiment of the present invention.
12 is a diagram illustrating a handover method for a case where a handover zone is set according to an embodiment of the present invention.
13 is a diagram of a wireless device (or communication node) in accordance with an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

In the present specification, duplicate descriptions are omitted for the same constituent elements.

Also, in this specification, when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, May be present. On the other hand, in the present specification, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that no other element exists in between.

Furthermore, terms used herein are used only to describe specific embodiments and are not intended to be limiting of the present invention.

Also, in this specification, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

Also, in this specification, the terms " comprise ", or " have ", and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, parts, or combinations thereof.

Also, in this specification, the term 'and / or' includes any combination of the listed items or any of the plurality of listed items. In this specification, 'A or B' may include 'A', 'B', or 'both A and B'.

Also, in this specification, a terminal is referred to as a mobile terminal, a mobile station, an advanced mobile station, a high reliability mobile station, a subscriber station, May refer to a mobile subscriber station, an access terminal, a user equipment (UE), or the like, and may refer to a terminal, a mobile terminal, a mobile station, an advanced mobile station, a high- A subscriber station, an access terminal, a user equipment, and the like.

Also, in this specification, a base station (BS) includes an advanced base station, a high reliability base station, a node B, an evolved node B, eNodeB, eNB), an access point, a radio access station, a base transceiver station, a mobile multihop relay (MMR) -BS, a relay station serving as a base station, BSs, Node Bs, eNodeBs, access points, wireless access stations, etc., may be referred to as high reliability relay stations, repeaters, macro base stations, A repeater, a high-reliability repeater, a repeater, a macro base station, a small base station, and the like.

First, a general handover method will be described. In this specification, the use of beamforming means that radio waves transmit and receive energy in a specific direction, not in all directions, during radio frequency (RF) transmission and reception. Particularly, in the case where the gain due to the beam forming is large, the beam forming has a valid meaning. The beamforming gain or antenna gain refers to the relative radiation that the beamforming antenna has for isotropic radiation. The unit of beamforming gain (or antenna gain) is dBi and is a unit of log size, so 10 dBi means 10 times and 20 dBi means 100 times. For example, when the beamforming gain is approximately 20 dBi, the beamforming gain is sufficiently large.

A handover procedure used in a long term evolution-advanced (LTE-A) system as a fourth generation mobile communication will be described as an example. A defined handover method is used regardless of whether beamforming is used or not. A relatively simple scenario in the handover scenario will be described as an example. For example, a mobility management entity (MME) and a serving gateway (S-GW) are maintained and only a base station is changed.

There is also a handover method based on X2 and a handover method based on S1 for the handover between base stations. A base station to which a terminal is currently connected is referred to as a source base station, and a base station to which a terminal is to be newly connected is referred to as a target base station.

The X2-based handover method is a method in which a direct data tunnel is formed between the source base station and the target base station, and downlink traffic flows from the source base station to the target base station, and then flows from the target base station to the mobile station.

In the S1-based handover method, a direct data tunnel is not formed between the source base station and the target base station, and an indirect data tunnel is formed in which the downlink traffic of the source base station flows to the target base station through the S-GW in the handover process Method.

The handover procedure can be divided into three steps or four steps. In the case where the handover decision is considered as a separate step, the handover procedure is divided into four steps. If the handover decision is included in the handover preparation step, the handover procedure is divided into three steps. The handover procedure is described in three steps as follows.

In the first step of the handover preparation step, the source base station performs a handover decision using the signal strength (or power) of the home cell reported by the terminal and the signal strength (or power) of the neighboring cell. When the source base station can select the handover scheme, the source base station selects one of the S1-based handover scheme and the X2-based handover scheme. Thereafter, the source base station informs the target base station of the handover and generates a GTP (general packet radio service tunneling protocol) tunnel to be used in the handover execution step (second step). A GTP tunnel is a path through which data flows temporarily.

In the second step of the handover execution step, the UE accesses a new base station (target base station), and downlink and uplink traffic flows through the GTP tunnel generated in the first step.

In the third step of the handover completion step, a normal path is formed through a new base station (target base station), and traffic flows through the path. The GTP tunnel, which is a temporary route, is removed. The above-described first to third steps are roughly described, and can be further subdivided according to the flow of the control signal.

Meanwhile, one of the requirements for the handover is the handover interruption time. On the other hand, an LTE (or LTE-A) system will be described with reference to FIG.

1 is a diagram illustrating a handover procedure for explaining a handover interruption time.

The handover interruption time is defined as the time taken to perform the processes S20 to S26 illustrated in FIG.

The terminal, the source base station, and the target base station perform handover preparation (S10).

When the mobile station receives a handover command from the source base station to perform handover, it performs internal processing (S11), and then performs radio synchronization with the target base station (S20). At this time, the source base station forwards the downlink traffic to the target base station.

The terminal performs a waiting procedure for transmitting a random access channel (RACH) on the uplink (S21).

The terminal transmits a RACH preamble to the target base station (S22).

When the target base station receives the RACH preamble, the target base station performs an internal process and transmits an acknowledgment to the RACH preamble (S23, S24).

When the terminal receives the RACH response, it performs internal processing (S25).

The target base station transmits the downlink data to the terminal (S26).

In LTE, an interruption time of 10.5 ms is defined for the frequency division duplex (FDD) method, and an interruption time of 12.5 ms is defined for the time division duplex (TDD) method. This does not represent all the time it takes to perform the handover, as described above. In the actual handover, the source base station forwards the data to the target base station, and after handover execution, the handover complete message must be transmitted between the target base station and the source base station. Therefore, the time taken to perform the handover is longer than the above-mentioned interruption time.

During the handover interruption time, data transmission must be stopped.

In case of a handover failure, the handover must be retried or a radio link recovery procedure must be performed, resulting in decreased data transmission efficiency. Therefore, a handover procedure or a handover algorithm that increases the handover success rate is needed. At the same time, there is a need to reduce the interruption time during handover.

Hereinafter, a handover method for a mobile communication system equipped with a beamforming antenna will be described. In the following, a method of performing a handover by a group mobile unit will be described. In the following, a handover method which is usefully applied to a system using beamforming with a high antenna gain will be described.

In the present specification, the group moving body refers to a moving body moving on a predictable route (predetermined route) while many people are riding such as a bus, a subway, a high-speed train, and the like.

A method (hereinafter referred to as a 'first method') in which a terminal used by a user existing in a group moving body (hereinafter referred to as 'terminal in a group mobile terminal') directly connects to an external cell can be used. That is, in the first method, a terminal in a group mobile terminal performs handover. Or a terminal in the group mobile terminal accesses the Internet via an AP in the group mobile terminal, and a separate communication device (hereinafter referred to as a "group mobile terminal communication device") mounted on the group mobile terminal accesses an external cell, (Hereinafter referred to as " second method ") can be used. That is, in the second method, the communication device in the group mobile terminal carries out the handover on behalf of the terminals in the group mobile terminal. Hereinafter, mainly the second method will be described as an example. However, this is merely an example, and the embodiment of the present invention can be applied to the first method. In this specification, the group moving body is connected to the cell may include that the communication device in the group moving body connects to the cell.

If a narrow RF beam and an antenna are used along the path of movement of the group moving body, a radio wave with a large propagation loss (for example, a millimeter wave) can reach a relatively large distance. For example, when the radio wave is designed to have a beam forming gain of about 20 dBi using a frequency of 30 GHz, the radio wave can reach up to 1 km, enabling communication maintaining a high transmission rate. In order to increase the beam-forming gain, the beam width becomes narrow. For example, the 3dB beam width may be less than 10 degrees.

On the other hand, in the case where an RF and an antenna to which beam forming is applied for a group moving body are used, a cell as shown in FIG. 2 can be constructed.

FIG. 2 is a diagram illustrating a cell configuration scenario when beamforming is applied to an RF and antenna for a group mobile station according to an embodiment of the present invention. FIG.

As illustrated in FIG. 2, the cell Cel1 and the cell Cel2 are formed by the RF and antenna device ANT1 to which beamforming is applied, and the RF and antenna device ANT2 to which beamforming is applied. The antenna ANT1 and the antenna ANT2 may be included in the same base station or may be included in different base stations. In the former case, the cell Cel1 and the cell Cel2 are formed by the same base station, and in the latter case, the cell Cel1 and the cell Cel2 are formed by different base stations. Hereinafter, embodiments of the present invention will be described by taking the case of the former as an example. However, this is merely an example, and in the latter case, the embodiment of the present invention can be applied.

2 shows a case in which the group moving body GM1 (e.g., high-speed train) moves in the right direction.

The group moving body GM1 can be connected to the cell Cel1 through the communication device in the group moving body GM1.

When the group moving body GM1 receives the radio wave from the antenna ANT1 and then passes the antenna ANT1, the intensity of the radio wave coming from the antenna ANT1 decreases sharply due to the characteristic of the narrow beam. In this case, the group moving body GM1 has to perform handover to the cell Cel2 configured by the antenna ANT2.

Depending on the characteristic of the narrow beam, the intensity of the radio wave may drop to 1/100 or less while the group moving body GM1 passes through the interval of about 10m. Therefore, it is helpful for the group moving body GM1 to perform the handover to the cell Cel2 stably in a short period of time, keeping the average data transmission rate high.

Depending on the speed of the group mobile, the time requirements for performing the handover may not be a major problem and vice versa. This will be described with reference to Table 1.

Given time (ms) Vehicle travel speed (km / h) 3 100 200 300 400 500 10 0.01m 0.3m 0.6m 0.8m 1.1m 1.4m 20 0.02 m 0.6m 1.1m 1.7m 2.2m 2.8m 30 0.03m 0.8m 1.7m 2.5m 3.3 m 4.2m 100 0.08m 2.8m 5.6m 8.3m 11.1m 13.9m 200 0.17m 5.6m 11.1m 16.7m 22.2m 27.8m 300 0.25m 8.3m 16.7m 25.0m 33.3m 41.7m 400 0.33m 11.1m 22.2m 33.3m 44.4m 55.6m 500 0.42m 13.9m 27.8m 41.7m 55.6m 69.4m

Table 1 shows the distance traveled by a moving object during a given time (e.g., 10 to 500 ms) when the speed of the moving object (e.g., vehicle) varies between 3 and 500 km / h.

In the case where the speed of the moving object is 3 km / h corresponding to the speed of the pedestrian, the moving distance of the moving object is less than 1 m for 10 to 500 ms, so that the moving object does not need to perform the handover as quickly.

However, when the speed of the moving object is 100 km / h, the moving object passes over the interval of 10 m or more for a time of 400 to 500 ms, so that the moving object may pass the above-mentioned section where the propagation intensity is suddenly decreased.

The higher the speed of the moving object, the greater the tendency. For example, when the moving object is the speed of the high speed train of 300 km / h, the moving object moves more than 8 m in 100 ms time. This means that the higher the speed of the group moving object, the more stable the handover should be performed at a faster time. For example, when a group moving body (GM1, for example, a high-speed train) moving at 300 km / h passes through a point (section) where the propagation intensity falls rapidly while passing through the antenna ANT1 of the cell Cel1, If handover is not performed and the group moving body GM1 can not connect to the cell Cel2, data reception becomes difficult.

The beamforming is applied, and the performance of the handover is very important in a cell for a high-speed group mobile object. Particularly, the group mobile terminal must perform handover at the correct timing and succeed in handover as soon as possible, thereby reducing data loss.

Hereinafter, a method for increasing the handover success rate in a cell to which beamforming is applied and thereby improving an average data transmission rate between a high-speed group mobile station and a terrestrial base station will be described.

1. Power distribution within a cell

When the group moving body GM1 is connected to the cell Cel1 and moves toward the cell Cel2 in the cell configuration scenario illustrated in Fig. 2, the antenna ANT1 for the cell Cel1 and the cell 3 to 6, a power distribution for a radio wave coming from the antenna ANT2 for the antenna Cel2 is explained.

3 is a three-dimensional representation of a beam pattern of an antenna. FIG. 4 is a diagram showing a secondary representation of the beam pattern of FIG. 3. FIG. 5 is a graph showing the power distribution when the height of the antenna installed on the ground is larger than the height of the receiving antenna provided on the mobile body. FIG. 6 is a diagram showing a case where the power distribution of FIG. 5 is enlarged.

In Fig. 3, the beam patterns of the antennas ANT1 and ANT2 are illustrated stereoscopically.

When the beam pattern of FIG. 3 is projected on one plane, it can be expressed in two dimensions, as illustrated in FIG.

In Fig. 4, simulated values and actual measured values are illustrated for frequencies 31.5 GHz and 32 GHz.

The power distribution depends not only on the beam pattern but also on the height of the antenna. 5 shows the case where the height of the antenna installed on the ground is 2 m larger than the height of the receiving antenna provided on the moving body (e.g., vehicle), the antenna ANT1 for the cell Cel1 is located 1,000 m, The antenna ANT2 is located at a position of 2,000 m. It is assumed that the directions of the antennas ANT1 and ANT2 are fixed in the horizontal direction. Accordingly, when the group moving body GM1 approaches the antennas ANT1 and ANT2, although the power (signal strength) increases as a whole, the power locally increases, decreases, increases again due to the influence of the beam pattern, Decrease.

When the power distribution at the 1,000 m point illustrated in Fig. 5 is enlarged, it is as illustrated in Fig. As illustrated in Fig. 6, the power variation near the antenna ANT1 for the cell Cel1 is well evident.

Considering how the terminal in the group mobile body GM1 or the communication device in the group mobile body GM1 (e.g., on-board device) performs handover in such a power distribution situation, establishing a handover procedure It is important.

2. Power distribution and Handover  Liver correlation

The power distribution illustrated in FIGS. 5 and 6 may vary according to the height of the antenna or the beam pattern of the beamforming antenna. However, when the group moving body GM1 approaches the antenna (for example, ANT1) The manner in which the power decreases sharply when the mobile unit GM1 passes the antenna (e.g., ANT1) is the same. On the other hand, the radio wave coming from the cell Cel2 has a form in which the distance is sufficiently large and increases very slowly.

It is conceptually shown in FIG. 7 that there is a slight difference in accordance with the beam pattern or the antenna height, but the above-described aspect is shown.

FIG. 7 is a diagram illustrating a signal intensity of a home cell and a signal intensity of a neighboring cell that change according to movement of a group moving body. Specifically, FIG. 7 is an enlarged view of the trend inside the rectangle at the center of the graph illustrated in FIG.

In Fig. 7, the signal strength (power) of the home cell is represented by a solid line, and the signal strength (power) of the neighboring cell is represented by a dotted line. Here, the home cell means the cell Cel1 currently connected to the group moving body GM1, and the neighboring cell means the cell Cel2 neighboring the cell Cel1.

The left interval INl1 is a section in which the power (or signal strength) of the home cell Cel1 is large around the power intersection point Pcr1 where the signal of the home cell Cel1 and the signal of the neighboring cell Cel2 cross each other .

The intensity of the signal received from the home cell Cel1 to the communication device in the group moving object GM1 (or the terminal in the group moving object GM1) is detected from the neighboring cell Cel2 to the group moving object GM1, Becomes equal to the intensity of the signal received by the internal communication device (or the terminal in the group moving object GM1).

In the left section IN11, it is difficult to search for the neighboring cell Cel2. The signal of the home cell Cel1 acts as an interference in the signal search for the neighboring cell Cel2.

On the other hand, in the right section INr1 of the power intersection Pcr1, the signal of the home cell Cel1 is abruptly decreased, so that the power serving as interference for the neighboring cell Cel2 search is rapidly reduced. That is, there is an advantage that it is easy to search for the neighboring cell Cel2. However, since the power of the home cell Cel1 drastically decreases, it becomes difficult to receive and decode the signal of the home cell Cel1 in the communication device in the group moving body GM1 or in the group moving body GM1. Therefore, the group moving body GM1 has to perform a handover to the neighboring cell Cel2 as soon as possible.

If the speed of the group mobile station GM1 is low, a sufficient time for handover is sufficient. However, if the group mobile unit GM1 moves at the speed of the high-speed railroad such as 300km / h, the group mobile unit GM1 passes the distance of about 8m within the time of 100ms. When the group moving body GM1 passes the crossing point Pcr1 for 10 m, the power of the home cell Cel1 is lowered and the signal quality becomes poor, which makes data reception difficult. Therefore, the group mobile unit GM1 must succeed by performing handover to the neighboring cell Cel2 as soon as possible, and the average data transmission rate can be kept high. To do this, it is necessary for the group moving body GM1 to perform a handover after the search for the neighboring cell Cel2 near the intersection Pcr1 as much as possible.

However, in a typical handover, the base station uses the power-related index of the home cell (Cel1) and the power-related index of the neighboring cell (Cel2) reported by the communication device in the group mobile body (GM1) , And determines whether or not the handover is performed. Here, the power related indicator includes a reference signal received power (RSRP). However, RSRP is not a very frequently measured and reported value. In LTE, the terminal is defined to measure RSRP at intervals of 200 ms and to report its value. How many times the RSRP is measured between 200ms and whether or not to average them can vary depending on the implementation.

It is not easy to find the power intersection Pcr1 between the home cell Cel1 and the neighboring cell Cel2 because the time of 200 ms is very long in terms of the group moving body (e.g., vehicle) moving at high speed. Therefore, a method for solving such problems is needed.

FIG. 8 is a diagram illustrating a cell configuration scenario when beamforming applied RF and antennas are used for group moving bodies according to another embodiment of the present invention. FIG.

Specifically, the cell configuration of the cell configuration scenario illustrated in FIG. 8 is the same as the cell configuration of the cell configuration scenario illustrated in FIG. 2, except that the moving direction of the group moving object GM1 corresponds to the moving direction of the group moving object GM1 It is the opposite.

2, a receiver for receiving radio waves from the cells Cel1 and Cel2 is mounted in front of the group moving body GM1, while a receiver for receiving radio waves from the cells Cel1 and Cel2 in the group And is mounted on the rear portion of the mobile body GM1.

The power distribution along the distance in the cell configuration scenario illustrated in FIG. 8 will be described with reference to FIG.

FIG. 9 is a diagram illustrating a signal strength of a home cell and a signal strength of a neighboring cell that change according to movement of a group moving object in the cell configuration scenario of FIG. 8. FIG.

In the cell configuration scenario illustrated in Fig. 8, the aspect of the power distribution along the distance is not different from the aspect of the power distribution illustrated in Figs. 5 and 6. However, since the moving direction of the group moving body GM1 is opposite, as illustrated in FIG. 9, the power of the home cell Cel1 is gradually lowered gradually, the power of the neighboring cell Cel2 is very weak, (ANT2) for the second antenna (Cel2).

9, the power intersection point Pcr2 between the home cell Cel1 and the neighboring cell Cel2 can be found.

The intensity of the signal received from the home cell Cel1 to the communication device in the group moving object GM1 (or the terminal in the group moving object GM1) is detected from the neighboring cell Cel2 to the group moving object GM1, Becomes equal to the intensity of the signal received by the internal communication device (or the terminal in the group moving object GM1).

The power of the home cell Cel1 is not high in the left interval INl2 of the power intersection Pcr2 but the power of the neighboring cell Cel2 is very weak and it is difficult to search for the neighboring cell Cel2.

When the group moving body GM1 crosses the power intersection Pcr2, the power of the home cell Cel1 is gradually reduced in the right section INr2 of the power intersection Pcr2, but the power of the neighboring cell Cel2 is sufficiently large , It is easy to search for the neighboring cell Cel2. Moreover, since the power of the home cell Cel1 is not sharply reduced, the urgency of the handover is less required than in the situation illustrated in Fig.

As described above, the power distribution according to the configuration of the cell affects the urgency of the handover of the group mobile unit GM1. Particularly, there is a difference in the requirements for the handover depending on whether the antennas ANT1 and ANT2 are on the front or rear sides of the group moving body GM1. Therefore, a method for solving such a problem is needed.

3. Handover  zone( zone )

As described above, when the base station antenna and the terminal antenna (or the antenna of the group moving body GM1) to which beamforming with a very high directionality is applied are used, the power crossing between the home cell Cel1 and the neighboring cell Cel2 In terms of characteristics, it differs from ordinary cellular mobile communication. Due to the strong directionality of the beam-forming antenna, the power at the cell boundary sharply decreases or rapidly increases. For example, as illustrated in FIG. 6, a power change of 20 dB may occur as the group mobile unit GM1 moves by 10 m.

In such a situation, a terminal or a group mobile station GM1 having high mobility must perform handover urgently. The high-speed train running at a speed of 300 km / h moves 8 m during 100 ms, so that the power of the home cell (Cel 1) falls sharply in a very short time. Therefore, in this case, it is necessary to perform and complete the handover before the group moving body GM1 moves away from the power intersections (e.g., Pcr1, Pcr2) between the home cell Cel1 and the neighboring cell Cel2.

However, in a typical handover procedure, the RSRP report period required for handover determination is long and the interval for averaging or filtering the RSRP value in the radio resource control (RRC) is long 200 ms in case of LTE), it is difficult for the base station to transmit the handover command at the correct timing. Hereinafter, an interval for averaging or filtering RSRP values is referred to as an RSRP averaging period.

It is effective to shorten the RSRP report period of the terminal in the group mobile body GM1 (or the communication apparatus in the group mobile body GM1) or the averaging period (or the filtering period) for the measurement in the RRC. However, Increases the head (overhead).

A method according to an embodiment of the present invention sets a handover zone for performing a handover from a home cell Cel1 to a neighboring cell Cel2 by a group moving body GM1 to which beamforming is applied, The RSRP reporting period of the terminal in the group moving object GM1 (or the communication device in the group moving object GM1) and the RSRP averaging period of the RRC are reduced. Thus, the method according to an embodiment of the present invention enables fast handover command delivery.

Also, the method according to the embodiment of the present invention reduces the RSRP reporting period and the RSRP averaging period again when the group moving object GM1 passes the handover zone. Accordingly, the method according to the embodiment of the present invention can alleviate the problem of overhead caused by frequent reports.

FIG. 10 is a diagram illustrating a case where a handover zone is set in a region where power (or signal strength) of a home cell is drastically reduced according to an embodiment of the present invention.

Specifically, the situation illustrated in Fig. 7 (a situation in which the power of the home cell Cel1 is rapidly reduced) can be assumed.

10, the graph Gh1 represents the power of the home cell Cel1, and the graph Gn1 represents the power of the neighboring cell Cel2. FIG. 10 illustrates a case where the handover zone Zho1 is set in a region where the power of the home cell Cel1 sharply decreases.

11 is a diagram illustrating a case where a handover zone is set in a region where the power of the home cell is gradually reduced but the power of the neighboring cell is rapidly increased according to an embodiment of the present invention.

Specifically, it can be assumed that the situation illustrated in Fig. 9 (the situation where the power of the home cell Cel1 is gradually reduced but the power of the neighboring cell Cel2 is rapidly increased).

11, the graph Gh2 represents the power of the home cell Cel1, and the graph Gn2 represents the power of the neighboring cell Cel2. 11 illustrates a case where the handover zone Zho2 is set in a region where the power of the home cell Cel1 is gradually reduced but the power of the neighboring cell Cel2 is rapidly increased.

4. Handover  Setting up the zone

In order to set the handover zone, it is very important to grasp the position of the power intersection point between the home cell Cel1 and the neighboring cell Cel2. That is, the handover zone can be set based on the power intersection point between the home cell Cel1 and the neighboring cell Cel2.

In the beamforming-based group mobile communication, it is necessary to set the handover zone through a method other than the power measurement because it is difficult to search for the neighboring cell before the power intersection point.

Specifically, since the cell boundary is formed in the vicinity of the beamforming antenna, a method of setting a handover zone based on the position (method M100) can be used. The method M100 forms a handover zone by grasping the positions of the terminals in the group moving body GM1 or the group moving body GM1. For example, in order to grasp the position of the terminal in the group moving body GM1 or the group moving body GM1, the terminal in the group moving body GM1 or the group moving body GM1 mounts a global position system (GPS) It is possible to compare the current position with the position information of the cells Cel1 and Cel2. That is, the terminal in the group mobile body GM1 or the group mobile body GM1 can determine whether the current position acquired through the GPS belongs to the handover zone.

The method of setting the handover zone without the GPS includes a method (method M200) of using timing advance information (TA) transmitted from the base station to the communication device in the group moving object GM1 (or the terminal in the group moving object GM1) . In general, a terminal must transmit a signal twice as much as a time proportional to a distance from a base station. Since the receiver of the base station receives a signal from a plurality of terminals in the cell, the receiver of the base station adjusts the terminal to match the start time of the transmission without receiving a signal in accordance with each terminal.

In the cell configuration scenario illustrated in Fig. 2, as the group moving body GM1 moves closer to the antenna ANT1, the TA value for the group moving body GM1 gradually decreases with time. On the other hand, in the cell configuration scenario illustrated in FIG. 8, as the group moving body GM1 moves and moves away from the antenna ANT1, the TA value for the group moving body GM1 gradually increases with time. Therefore, the method M200 can continuously monitor the TA value, determine the moving direction of the group moving object GM1 based on the variation pattern of the TA value, and set the handover zone using the TA value.

Hereinafter, a method M200 for setting a handover zone using TA will be described in detail.

In the random access, the base station measures the TA value using the random access preamble and then transmits the TA value to the communication device (or the terminal in the group mobile device GM1) in the group mobile device GM1. The TA value (initial TA value) in the random access response is always greater than or equal to zero. Here, the absolute propagation delay time of the radio wave from the antenna increases in proportion to the distance difference (the distance between the group moving object GM1 and the antenna). Therefore, the distance between the antenna and the communication device in the group moving object GM1 (or the terminal in the group moving object GM1) can be estimated based on the TA value. In LTE, the base unit is defined as 0.52us, which corresponds to a distance of 78m. In systems using millimeter waves, it is easy to reduce the base unit to about 1/10 of 0.52 us.

After random access, the base station measures the TA value using a sounding reference signal (SRS) rather than a random access preamble. Specifically, the base station increases or decreases the TA value (initial TA value) determined in the random access procedure, and then transmits the TA value to the communication device (or the terminal in the group moving object GM1) in the group moving object GM1. Therefore, the base station holds the initial position of the group moving body GM1 using the TA value (the TA value measured based on the random access preamble) based on the random access response and determines the TA value (based on SRS) (E.g., the distance between the group mobile body GM1 and the antennas ANT1 and ANT2) of the group moving body GM1 can be updated by using the TA value measured in the group moving body GM1.

First, the case where the TA value decreases (for example, the cell configuration scenario of FIG. 2) will be described as an example. If the measured TA value gradually decreases and becomes smaller than the reference TA value, the base station can determine that the group mobile unit GM1 has entered the handover zone. Here, the reference TA value may be about 1 us in the case of a system using millimeter waves.

When the group moving body GM1 enters the handover zone, at the same time, the base station activates a newly defined handover zone timer. For example, the base station can set the handover zone timer to Timer_HO_Zone = 0. TA is transmitted from the base station to the communication device in the group moving object GM1 or the group moving object GM1 so that the communication device in the group moving object GM1 (or the terminal in the group moving object GM1) An over-zone timer (Timer_HO_Zone) may be activated.

The communication device in the group mobile body GM1 (or the terminal in the group mobile body GM1) can reduce the RSRP report period and the base station can reduce the RSRP averaging period when the handover zone timer (Timer_HO_Zone) have. For example, the communication device in the group moving object GM1 (or the terminal in the group moving object GM1) can reduce the RSRP report period to about 1/10 to 1/100 of the RSRP report period for the normal case. Similarly, the base station can reduce the RSRP averaging period to about 1/10 to 1/100 of the RSRP averaging period for a typical case. Accordingly, the base station can transmit the handover command to the communication device (or the terminal in the group moving object GM1) in the group mobile body GM1 at a point near the power intersection Pcr1.

Next, the case where the TA value increases (for example, the cell configuration scenario in Fig. 8) will be described as an example. Whether or not the group moving body GM1 is at the cell boundary can be grasped through comparison between the distance corresponding to the measured TA value and a previously known distance (for example, a cell distance) when the measured TA value increases . That is, unlike the case where the TA decreases, the communication apparatus in the base station and the group mobile unit GM1 (or the terminals in the group mobile unit GM1) can transmit the coverage information of the current cell You need to receive.

The base station may store cell planning information and store the location of the antenna ANT2 of the neighboring cell Cel2 based on the antenna ANT1 of the home cell Cel1 which is the current cell. When the group moving body GM1 is connected to the home cell Cel1 which is the current cell, the base station transmits information about the neighboring cell Cel2 (e.g., the position of the antenna ANT2, the position between the antenna ANT1 and the antenna ANT2) Distance) can be transmitted to the communication device within the group moving body GM1 (or the terminal within the group moving body GM1). The base station uses the distance estimated from the measured TA value and the coverage information of the home cell Cel1 that is the current cell (e.g., the distance between the antennas ANT1 and ANT2) It is possible to judge whether or not it has entered. The subsequent procedure is the same as the above-described procedure in the case of TA decrease.

5. Handover  Procedure for setting up a zone

The handover algorithm for the beamforming-based high-speed group mobile station (GM1) requires standards and procedures related to the setting of the handover zone (e.g., specifications and procedures of the terminal and the base station).

First, a criterion for defining a handover zone is needed.

It is necessary that the reference TA value serving as a criterion of the handover zone needs to be defined when the TA is gradually reduced (for example, the cell configuration scenario of Fig. 2) as the group moving body GM1 moves toward the beam forming antenna ANT1 have. Hereinafter, the reference TA value is referred to as TA_HO_REF. TA_HO_REF can be determined according to the speed classification of group moving object (GM1). For example, TA_HO_REF applied to subways, trains, buses running at 100 km / h and TA_HO_REF applied to high-speed trains running at 300 km / h may be different. The movement time from the start point of the handover zone to the antennas ANT1 and ANT2 can be arranged as shown in Table 2 according to the speed of the group mobile unit GM1. At this time, it is assumed that the beamforming antennas ANT1 and ANT2 are on a straight path of the group mobile body GM1.

TA_HO_REF Street Movement time to antenna speed
100 km / h speed
300 km / h 1 us 150 m 5.4 sec 1.8 sec 0.67 us 100 m 3.6 sec 1.2 sec 0.33 us 50 m 1.8 sec 0.6 sec

In the setting of the handover zone, an appropriate TA_HO_REF can be selected according to the moving speed of the group moving body GM1 (e.g., the maximum moving speed). For example, when the moving speed of the group moving body GM1 is 300 km / h, TA_HO_REF can be determined to be about 1us, and when the moving speed of the group moving body GM1 is 100 km / h, TA_HO_REF is determined to be about 0.33us . The value of TA_HO_REF may be determined by the base station.

On the other hand, when the group moving body GM1 is moved away from the beam forming antenna ANT1 (for example, in the case of the cell configuration scenario of Fig. 8 and the receiving antenna is mounted at the rear portion of the group moving body GM1) , Information on a point at which the next antenna ANT2 is located is required. The bit width required to represent this information can be determined according to the degree of accuracy and range of cell coverage (or the distance between antennas).

For example, if the minimum unit of cell coverage is 10 m and the cell coverage is expressed up to 5,000 m, a cell coverage TA parameter TA_CELL_COV with 9 bits can be defined. TA_CELL_COV may have a TA value corresponding to cell coverage (e.g., distance between antennas ANT1 and ANT2). That is, TA_CELL_COV can be represented from 0 to 511, and TA_CELL_COV can be transmitted as configuration information for a cell. In this case, whether or not the group mobile body GM1 has entered the handover zone can be determined through comparison between (TA_CELL_COV - TA) and TA_HO_REF. For example, the base station can determine that the group mobile unit GM1 enters the handover zone when (TA_CELL_COV - TA) is smaller than TA_HO_REF.

The determination whether the group moving body GM1 has entered the handover zone can be performed by the base station having the TA information for the first time. In this case, the complexity for the handover zone entry decision does not increase at the communication device within the group mobile body GM1 (or within the group mobile body GM1).

Or whether the group moving body GM1 has entered the handover zone may be performed by the communication device in the group moving body GM1 (or the terminal in the group moving body GM1). In this case, the communication device in the group mobile body GM1 (or the terminal in the group mobile body GM1) can receive the TA value, TA_HO_REF, or TA_CELL_COV from the base station. In this case, the communication device in the group mobile body GM1 (or the terminal in the group mobile body GM1) can transmit the determination result about entry of the handover zone to the base station.

6. Handover  algorithm

The specifications and parameter definitions necessary for setting the handover zone are as described above. In addition, when the group moving body GM1 enters the handover zone, a procedure performed by the base station and the communication device within the group moving body GM1 (or the terminal within the group moving body GM1) needs to be defined.

If it is determined that the group moving body GM1 has entered the handover zone, the handover zone timer (Timer_HO_Zone) is set to 0 and Timer_HO_Zone is counted in accordance with the system clock to increase.

In order for the base station to transmit the handover command at an appropriate time, the RSRP averaging period of the RRC is shortened. Through this, power state monitoring for the home cell Cel1 and the neighboring cell Cel2 is performed at short intervals. For example, when the group moving body GM1 enters the handover zone, the RSRP averaging period can be adjusted to 2 ms, which is 1/20 of the RSRP averaging period (200 ms) defined in LTE, .

However, since this may increase the overhead of the system, the adjusted RSRP averaging period or the RSRP reporting period may be determined according to the speed classification of the group moving object GM1. Specifically, the higher the movement speed (e.g., the maximum movement speed) of the group mobile body GM1, the more the RSRP averaging period or the RSRP report period for the handover zone can be adjusted to a smaller value.

Meanwhile, the base station determines that the group mobile unit GM1 has entered the handover zone, and notifies the communication unit (or the terminal in the group mobile unit GM1) of the group mobile unit GM1. The communication device in the group moving object GM1 (or the terminal in the group moving object GM1) receiving the same adjusts its RSRP report period to be equal to the adjusted RSRP averaging period of the base station. In this case, the communication device in the group moving object GM1 (or the terminal in the group moving object GM1) does not need a separate implementation for determining the entry of the handover zone.

However, the communication device in the group moving body GM1 (or the terminal in the group moving body GM1) can independently perform the handover zone entry determination using additional information such as TA_CELL_COV and TA_HO_REF. In this case, there is an advantage that the communication device (or the terminal in the group mobile unit GM1) in the group mobile unit GM1, which is the subject of performing the RSRP report, can prepare quickly.

The RSRP reporting period of the communication apparatus in the group mobile unit GM1 (or the terminal in the group mobile unit GM1) is fast in the handover zone and the base station RRC can quickly make the handover decision decision using the RSRP report. Accordingly, when the speed of the group moving object GM1 becomes high, the handover procedure can be started at a time point as close as possible to the power intersection points (for example, Pcr1 and Pcr2).

The handover procedure needs to be completed within (Timer_HO_Zone <TA_HO_REF x 2). If the handover procedure is not completed within the range of (Timer_HO_Zone <TA_HO_REF x 2), the power of the home cell Cel1 is lowered so that the communication device in the group moving body GM1 (or the terminal in the group moving body GM1) The RSRP report period and the RSRP averaging period are returned to values before the group mobile station GM1 enters the handover zone.

Also, even if the handover procedure is successfully completed within (Timer_HO_Zone <TA_HO_REF x 2), the RSRP report period and the RSRP averaging period are reduced to values before the group mobile unit GM1 enters the handover zone. Through this, the system overhead can be reduced.

The above-described handover zone entry determination, handover command determination, handover execution, handover completion, and subsequent procedures will be described with reference to FIG.

12 is a diagram illustrating a handover method for a case where a handover zone is set according to an embodiment of the present invention.

In order to determine the entry of the handover zone, movement information of the group mobile unit GM1 is required. Specifically, it is determined whether the group moving body GM1 moves toward the beam forming antenna ANT1 (for example, the cell configuration scenario in Fig. 2) or the group moving body GM1 moves away from the beam forming antenna ANT1 ) Can be judged through the change of the TA. Such movement determination may be performed by the base station and may be performed by a communication device in the group mobile unit GM1 (or a terminal in the group mobile unit GM1). The result of this movement determination is likely to be that the group moving body GM1 does not change while the group moving body GM1 arrives to the final destination unless the group moving body GM1 is backward.

Fig. 12 exemplifies a case where the group moving body GM1 is determined to be close to the beam-forming antenna ANT1 after the movement determination is completed. However, this is only an example, and vice versa, a procedure similar to the procedure illustrated in Fig. 12 can be performed. For example, the procedure of comparing TA to TA_HO_REF (S110) may be replaced by a procedure of comparing (TA_CELL_COV - TA) with TA_HO_REF.

FIG. 12 illustrates a case where the processes of S100 to S150 are performed by the base station. However, this is only an example, and some or all of the processes of S100 to S150 may be performed by the communication device in the group mobile unit GM1 (or the terminal in the group mobile unit GM1).

The base station monitors whether the group mobile unit GM1 enters the handover zone (S100).

The base station determines whether the measured TA value is smaller than the TA_HO_REF value (S110).

If the measured TA value is smaller than the TA_HO_REF value, a procedure for entering the handover zone is started (S120). Specifically, the RRC of the base station shortens the RSRP averaging period. The base station informs the communication device within the group mobile body GM1 (or the terminal in the group mobile body GM1) that the group mobile body GM1 has entered the handover zone. Then, the base station sets a handover zone timer to 0 and performs an operation for handover. Here, the RSRP report period of the communication device in the group moving object GM1 (or the terminal in the group moving object GM1) can also be shortened.

The base station determines whether the handover is completed within a predetermined time (S130, S140). Specifically, the base station determines whether or not the communication device (or the terminal in the group moving object GM1) within the group moving object GM1 has succeeded within a handover from the home cell Cel1 to the neighboring cell Cel2 within (Timer_HO_Zone <TA_HO_REF x 2) can do.

When the handover is completed within (Timer_HO_Zone <TA_HO_REF x 2) or when the handover is not completed within (Timer_HO_Zone <TA_HO_REF x 2) (ie, when the time corresponding to TA_HO_REF x 2 has elapsed), the base station performs RSRP averaging The period is reduced to a value before the group moving body GM1 enters the handover zone (S150). Then, the base station informs the communication device (or the terminal in the group moving object GM1) in the group moving object GM1 that the group moving object GM1 is out of the handover zone. Here, the RSRP report period of the communication device in the group moving object GM1 (or the terminal in the group moving object GM1) can be reduced to a value before the group moving object GM1 enters the handover zone.

Meanwhile, among the handover procedures described herein, the procedures described as being performed by the base station (e.g., handover zone entry determination) are performed in the communication device (or group moving object GM1) in the group moving object GM1 Terminal).

13 is a diagram of a wireless device (or communication node) in accordance with an embodiment of the present invention. The radio equipment TN100 of FIG. 13 may be a base station, a terminal in the group mobile unit GM1, a communication unit in the group mobile unit GM1, or the like, described in this specification. Or the wireless device TN100 of FIG. 13 may be a transmitter or a receiver.

In the embodiment of FIG. 13, the wireless device TN100 may include at least one processor (TN 110), a transceiver (TN 120) in communication with the network, and a memory (TN 130). Further, the radio device TN100 may further include a storage device TN140, an input interface device TN150, an output interface device TN160, and the like. The components included in the wireless device TN100 may be connected by a bus (TN170) and communicate with each other.

The processor TN110 may execute a program command stored in at least one of the memory TN130 and the storage device TN140. The processor TN110 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which methods according to embodiments of the present invention are performed. The processor TN110 may be configured to implement the procedures, functions, and methods described in connection with the embodiments of the present invention. The processor TN110 may control each component of the wireless device TN100.

Each of the memory TN130 and the storage device TN140 may store various information related to the operation of the processor TN110. Each of the memory TN130 and the storage device TN140 may be constituted of at least one of a volatile storage medium and a nonvolatile storage medium. For example, the memory TN130 may be configured with at least one of a read only memory (ROM) and a random access memory (RAM).

The transceiver apparatus TN120 can transmit or receive a wired signal or a wireless signal. And the wireless device (TN100) may have a single antenna or multiple antennas.

On the other hand, the embodiments of the present invention are not only implemented by the apparatuses and / or methods described so far, but may also be realized through a program realizing a function corresponding to the configuration of the embodiment of the present invention or a recording medium on which the program is recorded And such an embodiment can be easily implemented by those skilled in the art from the description of the embodiments described above.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

Claims (20)

A method for performing a handover for a communication device in a base station, the method comprising:
Measuring a timing advance (TA) using a signal received from the communication device;
Determining whether the mobile has entered a handover zone using the measured TA and the reference TA; And
Decreasing an RSRP averaging period for averaging a reference signal received power (RSRP) from a first value to a second value when the mobile device enters the handover zone
And a handover method of the base station. The method according to claim 1,
Wherein the step of determining whether the mobile has entered the handover zone comprises:
And determining a moving direction of the moving body based on the measured variation pattern of TA
A base station handover method. 3. The method of claim 2,
Wherein the step of determining the moving direction of the moving object comprises:
Determining that the moving object is moving toward the first antenna for the first cell to which the communication device is connected if the measured change pattern of the TA indicates that the measured TA decreases with time; And
And determining that the moving object is moving away from the first antenna when the measured variation pattern of TA indicates that the measured TA increases with time
A base station handover method. The method according to claim 1,
Wherein the step of determining whether the mobile has entered the handover zone comprises:
And determining that the mobile has entered the handover zone when the mobile moves toward the first antenna for the first cell connected to the communication device and the measured TA is smaller than the reference TA doing
A base station handover method. The method according to claim 1,
Wherein the step of determining whether the mobile has entered the handover zone comprises:
Determining whether the following equation (1) is satisfied when the mobile body moves away from the first antenna for the first cell connected to the communication device; And
And determining that the mobile has entered the handover zone when Equation (1) is satisfied
A base station handover method.
[Equation 1]
(TA_CELL_COV - TA_M) <TA_HO_REF
(TA_M corresponding to the measured TA, TA_CELL_COV: TA corresponding to the distance between the first antenna and the second antenna for the second cell neighboring the first cell, TA_HO_REF: the reference TA) 5. The method of claim 4,
The reference TA is determined according to the moving speed of the moving object
A base station handover method. 5. The method of claim 4,
Wherein the first antenna is a beam-forming antenna for the moving object
A base station handover method. The method according to claim 1,
Wherein the second value is a value that is smaller as the moving speed of the moving object is higher
A base station handover method. The method according to claim 1,
The step of reducing the RSRP averaging period comprises:
And informing the communication device that the mobile has entered the handover zone to reduce the RSRP reporting period of the communication device
A base station handover method. The method according to claim 1,
The step of reducing the RSRP averaging period comprises:
Resetting a first timer; And
And using the first timer to determine whether the communication device has successfully handed over from the first cell to the second cell within a time corresponding to twice the reference TA
A base station handover method. The method according to claim 1,
And returning the RSRP averaging period to the first value when handover of the communication apparatus is successful
Further comprising the steps of: The method according to claim 1,
In the handover zone,
Is set based on a power intersection point at which the intensity of the signal received from the first cell to which the communication device is connected to the communication device is equal to the intensity of the signal received from the second cell neighboring the first cell to the communication device
A base station handover method. The method according to claim 1,
The measuring step;
Measuring a first TA based on a random access preamble received from the communication device; And
Measuring a second TA based on a sounding reference signal (SRS) received from the communication device,
Wherein the step of determining whether the mobile has entered the handover zone comprises:
Determining the moving direction of the moving body using the first TA and the second TA,
A base station handover method. A method for performing a handover on behalf of a plurality of terminals existing in a moving body,
Transmitting at least one of a random access preamble and a sounding reference signal (SRS) to a base station for TA (timing advance) measurement; And
Reducing a reference signal received power (RSRP) report period from a first value to a second value when it is determined that the mobile has entered a handover zone based on the measured TA;
And a handover method of the communication device. 15. The method of claim 14,
The step of reducing the RSRP report period comprises:
And determining whether the mobile has entered the handover zone using a reference TA determined according to the moving speed of the moving object and the measured TA
A method of handover of a communication device. 15. The method of claim 14,
Prior to the reducing step,
Receiving from the base station a cell coverage TA corresponding to a distance between a first antenna for a first cell connected to the communication device and a second antenna for a second cell neighboring the first cell,
The method comprising the steps of: 16. The method of claim 15,
Further comprising returning the RSRP report period to the first value if the handover is successful within a predetermined time,
Wherein the predetermined time corresponds to twice the reference TA
A method of handover of a communication device. Memory; And
And a processor connected to the memory and performing a handover for a mobile entity in which a plurality of terminals exist,
The processor comprising:
Receiving at least one of a random access preamble (SRS) and a sounding reference signal (SRS) from a communication apparatus mounted in the moving body, measuring a timing advance (TA) using the received signal, The base station determines whether the mobile has entered a handover zone for performing a handover from the first cell to the second cell using the reference TA and the measured TA
Base station. 19. The method of claim 18,
The processor comprising:
Wherein the RSRP averaging period for averaging a reference signal received power (RSRP) is reduced from a first value to a second value when the mobile unit enters the handover zone, It is determined whether or not the handover of the communication device is successful within the first time
Base station. 20. The method of claim 19,
The processor comprising:
When the handover of the communication device succeeds within the first time or when the first time has elapsed, the RSRP averaging period is returned to the first value
Base station.

Images